1. Field of the Invention
The present invention relates to an ink composition, an ink set, and an image forming method.
2. Description of the Related Art
In recent years, various materials have been used as media for ink jet recording, for example, as well as dedicated ink jet paper, media for printing such as commercially available plain paper, high-quality paper, coated paper, and art paper, have come into use. Whichever material is to be recorded upon, there is a demand for high-grade image quality.
Also, in such cases as using plain paper and printing media, a pigment is preferable as an ink coloring material capable of forming a highly robust image having water resistance and light resistance and the like. Among inks including pigments, there is interest in water-based pigment inks from the viewpoints of cost and the global environment or the safety of business environment and the like. Among these, as magenta pigment for ink jet applications, quinacridone-based pigments have been suitably used.
As water-based ink for ink jet recording, there is disclosed an aqueous dispersion of water-insoluble vinyl polymer particles containing quinacridone-based pigments such as C.I. Pigment Red 122 and/or C.I. Pigment Violet 19 and a pigment derivative having a quinacridone skeleton in which an acidic group has been introduced into an organic pigment (for example, refer to JP2006-176623A). Further, there is disclosed a water-based ink containing a quinacridone solid solution pigment contained in cross-linked polymer particles (for example, refer to JP2009-275125A). However, the ink cannot be stably maintained in these configurations.
In consideration of the above-described situation, there is disclosed an aqueous ink for ink jet recording containing a quinacridone solid solution pigment including two types or more of quinacridone compounds and including cross-linked polymer particles having an anionic group neutralized with a base (for example, refer to JP2009-46595A). According to the literature, the chroma is increased and the storage stability is improved.
In addition, there is disclosed aqueous active energy ray-curable ink containing a water-soluble photopolymerizable material undergoing radical polymerization, a specific water-soluble photopolymerization initiator, and an anionic aqueous pigment dispersion (for example, refer to JP2009-102454A). Further, there is disclosed an aqueous ink composition including a water-soluble polymerizable compound, a photopolymerization initiator, and a water-insoluble coloring material (for example, refer to JP2011-105826A), and a quinacridone solid solution pigment may be exemplified as such a water-insoluble coloring material.